U.S. patent number 6,846,848 [Application Number 10/226,752] was granted by the patent office on 2005-01-25 for production of high purity fisher-tropsch wax.
This patent grant is currently assigned to ExxonMobil Research and Engineering Company. Invention is credited to Loren Leon Ansell, Louis Francis Burns, Daniel Francis Ryan, Robert Jay Wittenbrink.
United States Patent |
6,846,848 |
Wittenbrink , et
al. |
January 25, 2005 |
**Please see images for:
( Certificate of Correction ) ** |
Production of high purity fisher-tropsch wax
Abstract
A hydrocarbon wax product from a hydrocarbon synthesis slurry
comprising liquid synthesis product and catalyst particles is
purified by introducing a portion of hydrocarbon synthesis slurry
from a hydrocarbon synthesis zone to a treatment zone in which a
treatment gas contacts the hydrocarbon synthesis slurry. Hydrogen
or a hydrogen-containing gas is useful as the treatment gas. The
gas treatment removes impurities from the hydrocarbon wax portion
of the hydrocarbon synthesis slurry. Purified wax product is
separated and removed in situ via wax withdrawal means. This avoids
or minimizes the need for further treating the wax product.
Inventors: |
Wittenbrink; Robert Jay
(Kingwood, TX), Ansell; Loren Leon (Baton Rouge, LA),
Ryan; Daniel Francis (Baton Rouge, LA), Burns; Louis
Francis (Baton Rouge, LA) |
Assignee: |
ExxonMobil Research and Engineering
Company (Annandale, NJ)
|
Family
ID: |
25420465 |
Appl.
No.: |
10/226,752 |
Filed: |
August 23, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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905232 |
Jul 13, 2001 |
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Current U.S.
Class: |
518/700; 518/709;
518/715 |
Current CPC
Class: |
C10G
2/342 (20130101); B01J 8/228 (20130101); C10G
2/32 (20130101) |
Current International
Class: |
B01J
8/22 (20060101); B01J 8/20 (20060101); C10G
2/00 (20060101); C07C 027/00 () |
Field of
Search: |
;518/700,709,715 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0967262 |
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Dec 1999 |
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EP |
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WO 9850485 |
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Nov 1998 |
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WO |
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WO 9850489 |
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Nov 1998 |
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WO |
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WO 9850490 |
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Nov 1998 |
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WO |
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WO 9937736 |
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Jul 1999 |
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WO |
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WO 9941217 |
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Aug 1999 |
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WO |
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WO 02076600 |
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Oct 2002 |
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WO |
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Primary Examiner: Parsa; J.
Attorney, Agent or Firm: Marin; Mark D.
Parent Case Text
This application is a Continuation-In-Part of U.S. Ser. No.
09/905,232 filed Jul. 13, 2001, now abandoned.
Claims
What is claimed is:
1. A process for forming a hydrocarbon wax product comprising (a)
reacting a synthesis gas comprising a mixture of H.sub.2 and CO in
the presence of a solid, particulate hydrocarbon synthesis catalyst
in a hydrocarbon synthesis shiny comprising said catalyst and a
hydrocarbon liquid in a hydrocarbon synthesis zone of a reactor
under reaction conditions effective to form a liquid hydrocarbon
wax, said hydrocarbon liquid comprising said liquid hydrocarbon
wax; (b) introducing a portion of said hydrocarbon synthesis shiny
containing the liquid hydrocarbon wax into a treatment zone; (c)
contacting said portion of said hydrocarbon synthesis shiny in said
treatment zone with a hydrogen-containing treatment gas to form a
treated slurry, said treated shiny comprising said catalyst
particles and a treated hydrocarbon liquid, comprising a purified
hydrocarbon wax; and, (d) separating the hydrocarbon wax from said
treated slurry.
2. The process of claim 1 further including the step of
re-introducing said treated slurry into said hydrocarbon synthesis
zone.
3. The process of claim 2, wherein said treatment gas comprises
hydrogen.
4. The process of claim 1, further including the step of
introducing said treated slurry to gas disengaging means prior to
separating said treated slurry from the treated wax.
5. The process according to claim 3 wherein said treatment zone and
said separating are external to said reactor.
6. The process of claim 5 wherein said separating means comprises a
tubular filter member surrounded by a larger diameter outer member
forming an annular space therebetween, wherein said filter member
has a semi-permeable wall that is permeable to said purified
hydrocarbon wax and impermeable to said catalyst.
7. The process of claim 6 wherein said semi-permeable wall
comprises sintered metal.
8. The process of claim 5 wherein said catalyst comprises a
supported Group VIII metal.
9. The process of claim 8 wherein said metal comprises cobalt.
10. The process of claim 9 wherein said support includes titania,
alumina, or silica-alumina.
Description
FIELD OF THE INVENTION
The present invention relates to a slurry type hydrocarbon
synthesis process in which impurities are removed in situ from a
hydrocarbon slurry liquid comprising the raw wax product of the
hydrocarbon synthesis reaction.
BACKGROUND OF THE INVENTION
Hydrocarbon synthesis (HCS) methods utilizing Fischer-Tropsch
processes are well known and described in the art. In a
Fischer-Tropsch process, synthesis gas (CO+H.sub.2) made, e.g. from
natural gas, is converted over a catalyst, e.g. a ruthenium, iron,
or cobalt catalyst, to form a wide range of products including
gaseous and liquid hydrocarbons, oxygenates and a normally solid,
high paraffin hydrocarbon wax. Typically, Fischer-Tropsch waxes are
upgraded by catalytically converting them to lower boiling
paraffinic hydrocarbons falling within the gasoline and middle
distillate boiling ranges. This treatment primarily involves
hydrogenation, e.g. hydroisomerization, hydrocracking,
hydrorefining and the more severe hydrorefining referred to as
hydrotreating. However, as new markets expand, the demand for high
quality waxes as end products has increased. The varied and growing
uses for high quality Fischer-Tropsch waxes include e.g. food
containers, waxed paper, coating materials, electrical insulators,
candles, crayons, markers, cosmetics, etc. Stringent purity
requirements that a wax must meet are set by regulatory authorities
such as the FDA in the United States and the SCF in the European
Union, particularly if the wax is to be used in food and drug
applications.
Fischer-Tropsch waxes have many desirable properties. They have
high paraffin contents and are essentially free of the sulfur,
nitrogen and aromatic impurities found in petroleum waxes. However,
untreated raw Fischer-Tropsch waxes may contain small but
significant quantities of olefins and oxygenates (e.g. long chain
primary alcohols, acids and esters) formed in the slurry as by
products of the HCS reaction. Consequently, there is a need to
further treat raw Fischer-Tropsch wax to remove these impurities.
This additional treatment is part of a time consuming and costly
process as Fischer-Tropsch waxes typically undergo hydroprocessing
in order to achieve high purity. These purification measures
typically occur in another reactor separate from the reactor where
the hydrocarbon synthesis has occurred. In addition, different
catalysts are used to hydroprocess the wax. Accordingly, there is a
need for a more efficient and direct method of producing purified
Fischer-Tropsch wax from a hydrocarbon synthesis process.
A preferred process mode for operating the Fischer-Tropsch process
is a slurry-type process which may be carried out, e.g. in moving
bed systems or slurry reactors. The slurry comprises slurry liquid
and finally divided catalyst, wherein the catalyst particles are
suspended in a liquid hydrocarbon and the CO/hydrogen mixture is
forced through the catalyst/hydrocarbon slurry allowing good
contact between the CO/hydrogen and the catalyst to initiate and
maintain the hydrocarbon synthesis process.
Advantages of a slurry-type process, over that of a fixed bed
process are that there is better control of the exothermic heat
produced in the Fischer-Tropsch process during the reaction and
better control over catalyst activity maintenance by allowing
recycle, recovery, and rejuvenation procedures to be implemented.
The slurry process can be operated in a batch or in a continuous
cycle, and in the continuous cycle, the entire slurry can be
circulated in the system allowing for better control of the primary
products' residence time in the reaction zone.
Slurry reactors, sometimes referred to as "bubble columns," are
well known for carrying out highly exothermic, three phase
slurry-type Fischer-Tropsch reactions. As disclosed in U.S. Pat.
No. 5,348,982, in a three-phase hydrocarbon synthesis (HCS)
process, a synthesis gas comprising a mixture of H.sub.2 and CO
(syngas) is bubbled up as a third, gaseous phase through the slurry
in the reactor. The slurry comprises liquid hydrocarbons and
dispersed solid particles comprising a suitable Fischer-Tropsch
type hydrocarbon synthesis catalyst. The catalyst particles are
typically kept dispersed and suspended in the liquid by the lifting
action of the syngas bubbling up through the slurry and by
hydraulic means. Typically, the slurry liquid is the product of the
reaction, usually C.sub.5 -C.sub.100 hydrocarbons. Preferably, the
slurry liquid comprises primarily high boiling paraffins
(Fischer-Tropsch waxes).
SUMMARY OF THE INVENTION
The present invention relates to a method for treating and
separating purified Fischer-Tropsch wax in situ from the
catalyst/hydrocarbon mixture produced in a hydrocarbon synthesis
process. The catalyst/hydrocarbon mixture, referred to herein as
the "slurry" comprises catalyst particles and slurry liquid. The
slurry liquid comprises the products of the hydrocarbon synthesis
reaction, primarily Fischer-Tropsch waxes. In one embodiment, a
portion of slurry produced in a hydrocarbon synthesis process is
passed from a hydrocarbon synthesis reaction zone into a treatment
zone where it is contacted with treatment gas, preferably hydrogen
or hydrogen-containing gas. Contact with the treatment gas removes
impurities such as oxygenates or olefins from the slurry liquid,
e.g., by converting them to hydrocarbons. The treatment gas
injected into the treatment zone preferably comprises hydrogen and
may contain other gases such as nitrogen, CO.sub.2, H.sub.2 O,
CH.sub.4, C.sub.2 -C.sub.4 hydrocarbons, and also CO (as long as
the mole ratio of the H.sub.2 to CO is sufficient to remove the CO
and still remove at least a portion of the impurities from the
wax). In another embodiment, all or a portion of the treatment gas
may be recycled back into the treatment zone after it has been
treated to remove oxygenates and other impurities such as nitrogen
so as not to re-contaminate the treated wax. Optionally, the
treatment gas acts as a lift gas and may aid in removing
de-activating species which degrade catalyst activity in the
slurry. The gas treated slurry is passed through a wax withdrawal
means, such as a filter, where a portion of purified, slurry,
liquid wax product is drawn off and recovered. The recovered wax
product is passed to storage, sold as end product, further upgraded
if necessary, etc. In a preferred embodiment, off-gases produced
during the gas treatment are removed from the treated slurry prior
to passing it to wax withdrawal means. Reducing the gas content of
the circulating treated slurry results in greater liquid throughput
through the wax withdrawal means and prevents off-gas from
re-contaminating the hydrocarbon synthesis reaction in the
synthesis one.
With specific regard to a slurry-type hydrocarbon synthesis process
form forming Fischer-Tropsch waxes, at least a portion of which are
liquid at the reaction conditions, the invention comprises the
steps of: (a) reacting a synthesis gas comprising a mixture of
H.sub.2 and CO in the presence of a solid, particulate hydrocarbon
synthesis catalyst in a slurry comprising said catalyst and a
hydrocarbon liquid in a Fischer-Tropsch reactor synthesis zone
under reaction conditions effective to form a liquid hydrocarbon
wax, said hydrocarbon liquid comprising said liquid hydrocarbon
wax; (b) passing a portion of said slurry from said synthesis zone
to a treatment zone; (c) contacting said slurry in said treatment
zone with a treatment gas to form a treated slurry, said treated
slurry comprising said catalyst particles and a purified
hydrocarbon liquid product comprising a purified hydrocarbon wax;
(d) passing said treated slurry through wax withdrawal means to
separate and withdraw a portion of said purified hydrocarbon wax
from said treated slurry; and, (e) passing the remainder of the
treated slurry back into the synthesis zone.
Treatment gas is preferably hydrogen or hydrogen-containing gas. In
one embodiment, the treated slurry is passed through gas
disengagement means in which off-gas produced in step c) is removed
from the treated slurry before the purified hydrocarbon wax is
separated and withdrawn.
In the context of the invention, the term "slurry" refers to a
mixture of solid catalyst particles and hydrocarbon liquid in a
slurry-type hydrocarbon synthesis process. The catalyst is any
suitable Fischer-Tropsch catalyst and the hydrocarbon liquid
comprises the hydrocarbon product of the hydrocarbon synthesis
process, primarily high boiling liquid paraffin wax. The term
"impurities" refers to oxygenates, (i.e. primary and secondary
alcohols, acids, esters or mixtures thereof), olefins and the like
in the hydrocarbon liquid which are removed by contact with a
treatment gas, e.g. by contacting them with hydrogen or
hydrogen-containing gas and converting them to hydrocarbons. As
used herein, "catalyst deactivating species" is meant to include
species that degrade catalyst activity. Such deactivating species
are removed by contact with the same treatment gas that serves to
remove impurities from the liquid hydrocarbon wax product of the
Fischer-Tropsch reaction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic representation of a process in accordance
with the present invention.
FIG. 2 shows a schematic representation of an alternative
embodiment of the process in accordance with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, a hydrocarbon wax product from
a hydrocarbon synthesis slurry comprising liquid synthesis product
and catalyst particles is purified by circulating the slurry from a
hydrocarbon synthesis zone in a Fischer-Tropsch reactor through a
treatment zone in which a treatment gas contacts the slurry.
Hydrogen or a hydrogen-containing gas is useful as the treatment
gas. Other gases may be present, including light hydrocarbons, e.g.
CH.sub.4, C.sub.2 H.sub.6, or nitrogen; however, care should be
taken to avoid known Fischer-Tropsch catalyst poisons, e.g. H.sub.2
S. The gas treatment removes impurities from the liquid hydrocarbon
wax product and also removes catalyst de-activating species which
may be present in the slurry. Purified wax product is separated
from the treated slurry and removed from the process via wax
withdrawal means. This avoids or minimizes the need for further
treatment of the wax product. The remaining treated slurry may be
passed back into the hydrocarbon synthesis zone.
The hydrocarbon synthesis reactor will typically be operating
during treatment and filtration and may be continuous or
intermittent. The wax treatment process does not interrupt the
hydrocarbon synthesis reaction taking place in the hydrocarbon
synthesis zone of the Fisher-Tropsch reactor. While the treatment
zone is separate from the synthesis zone, it may optionally be
located within the synthesis zone. In preferred embodiments,
however, the treatment zone is housed in a separate unit outside of
the reactor and is connected to the reactor by conduits within
which a portion of slurry from the synthesis zone circulates. By
using separate units to house the synthesis zone and the treatment
zone, it is not necessary that slurry treatment by conducted at the
same reaction conditions as the Fisher-Tropsch reaction within the
synthesis zone. Conditions such as temperature may be independently
regulated as disclosed in co-pending U.S. Ser. No. 905,231.
When separate reaction units are used, it is preferred that the
units housing the treatment zone have isolation means, such as
valves in the connecting conduits which enable it to be isolated
from the reactor. This isolation feature permits separate repair
and maintenance. Likewise, it is preferable for the wax withdrawal
means to be housed separately from the synthesis reaction zone,
thus allowing separate maintenance, e.g. filter removal and
replacement without having to take the HCS reactor off-line. This
allows operation on a continuous basis with each process being
performed at optimal, uninterrupted conditions. In U.S. Pat. No.
5,260,239, Hsia discloses a process for removing a portion of
slurry comprising degraded catalyst in liquid synthesis product
from the hydrocarbon synthesis zone of a Fischer-Tropsch reactor,
removing catalyst de-activating species in an external rejuvenation
vessel and then returning the slurry containing rejuvenated
catalyst to the main slurry body in the Fischer-Tropsch reactor.
However, rejuvenation and recycling of Fischer-Tropsch catalyst
does not address the treatment of the slurry liquid comprising
Fischer-Tropsch wax product for removal of impurities.
Additionally, the recycling method disclosed by Hsia does not
provide for removal of a portion of treated Fischer-Tropsch wax
product prior to recycling the rejuvenated catalyst back into the
hydrocarbon synthesis zone.
One embodiment of the invention is illustrated in schematic cross
section in FIG. 1 wherein synthesis gas is introduced into a
slurry-type Fischer-Tropsch reactor 10 and maintained at reaction
temperature and pressure. Pressures typically range from 5-30 bar,
more preferably 10-25 bar. Temperatures may range from about
193-232.degree. C., preferably 199-230.degree. C. Molar hydrogen to
carbon monoxide ratios in the feed gas may range from about
1.5:1-2.5:1, preferably about 1.9:1-2.2:1.
Slurry reactor 10 comprises a hollow shell 12 housing a hydrocarbon
synthesis reaction zone 17 with hydrocarbon synthesis slurry 14
within. The slurry 14 comprises solid catalyst particles and
hydrocarbon liquid. The slurry liquid comprises HCS reaction
products which are liquid at the slurry reaction conditions,
preferably Fischer-Tropsch waxes with small amounts of primary and
secondary alcohols, acids, esters, olefins or mixtures thereof. Gas
reaction products of the hydrocarbon synthesis reaction escape
slurry 14 and collect in gas collection space 26. Gas inlet line 16
feeds a syngas into the reactor and up into the bottom of the
slurry through suitable gas distribution means 18 at the bottom of
the slurry. Gas distribution means injects the gas up into the
bottom of slurry in which it rises as gas bubbles indicated by the
small circles. Unreacted synthesis gas escapes the slurry and also
collects in gas collection space 26 in the top of the reactor and
is removed via gas product line 22.
Hydrocarbon liquid withdrawal means 41, such as a filter, is
located within the synthesis zone 17 for withdrawing hydrocarbon
product (i.e. raw Fischer-Tropsch wax) from the reactor 10 via line
29. Conduit 11 exits the reactor and extends over laterally as
transverse portion 43, which turns upward into hollow lift pipe 47
and is in fluid communication with interior treatment zone 20 of
lift pipe. Shut-off valve 29 in transverse portion 43 of conduit 11
allows the treatment zone to be isolated from reactor 10 if
desired.
Thus, liquid Fischer-Tropsch wax in the presence of catalyst
particles disengages from the gaseous product in the reactor 10 and
falls under its own weight as a slurry into collecting cup 5 and
enter conduit via orifice 49 which is in fluid communication with
conduit 11. After exiting the reactor the slurry then passes over
and into the interior treatment zone 20 of lift pipe 47. Treatment
gas comprising hydrogen is passed via line 51 into the interior of
lift pipe 47 near the bottom thereof, in which it contacts the
circulating slurry to remove impurities such as olefins and
oxygenates (i.e. primary and secondary alcohols, acids, esters or
mixtures thereof) from the liquid wax phase. Optionally,
hydrocarbon synthesis product from line 19 (i.e. untreated
Fischer-Tropsch wax) may be recycled via line 22 such that it
enters the interior of lift pipe 47 for treatment. Treatment gas
may also removes catalyst deactivating species and may act as a
lift gas to lift the treated slurry up over and out of the upper
opening 53 and into optional gas disengaging means 26 comprising
vessel 8. In gas separating means the off-gas produced during
treatment escapes from the treated slurry into collection zone 23
and is removed via gas line 54. This offgas is consumed as fuel or
sent to further processing.
Disengaged from the offgas, liquid wax and catalyst particles fall
into the bottom portion of vessel 8 as a gas-reduced treated slurry
which is in fluid communication with tubular conduit 9 via orifice
31. The gas-reduced treated slurry flows down through tubular
conduit 9 into wax withdrawal means 30. In this embodiment, wax
withdrawal means 30 comprises a portion of conduit 9 which is
surrounded and enclosed by a larger diameter outer conduit 33
defining annular space 35 therebetween. In that portion adjacent to
annular space 35, conduit 9 has a semi-permeable wall 13 through
which liquid wax but not catalyst particles may pass.
Semi-permeable wall 13 is comprised of e.g. fine meshed screen,
helically wound threads or, preferably, sintered metal particles.
Treated slurry flows through orifice 31 into the interior of
conduit 9 where a portion of the purified liquid wax phase passes
out of the interior through semi-permeable wall 13 into annular
space 35 as product. Thus, purified wax product is separated from
the treated slurry as it passes through the interior of conduit 9.
Purified wax product is removed from the process via line 15 which,
in this embodiment, is in fluid connection with annular space 35.
Treated slurry remaining in the interior of semi-permeable wall 13
passes back into hydrocarbon synthesis reaction zone 17 of reactor
10 via conduit 50 and orifice 52. Shutoff valve 67 allows reactor
10 to be isolated from the external units, if necessary, e.g. for
separate maintenance and repair.
Any suitable means for separating wax product from a mixture of
liquid wax and catalyst particles is useful for withdrawal of the
purified wax product of the present invention. For example, FIG. 2
shows an alternate embodiment wherein purified wax product may be
separated via withdrawal means 70, such as a filter, located within
gas disengaging vessel 8 and removed via line 72. Like parts are
like numbered to those in FIG. 1.
The removal of impurities from circulating hydrocarbon liquid in
the present invention process is demonstrable by measuring
differences in the levels of selected impurities in Fischer-Tropsch
wax drawn from a HCS reactor with external treatment means when
such means are in an operating mode and in a non-operating mode.
Infrared spectroscopy can be used for determining olefin and
selected oxygenate concentrations in the wax product. In the
examples that follow, esters were selected for measurement since
they are typically the most difficult molecules to hydrogenate
relative to the other species (e.g., acids or olefins) in
Fischer-Tropsch wax. The ester content is determined using infrared
spectroscopy by rationing an ester peak to a hydrocarbon overtone
band and subsequently multiplying the ratio by a factor derived
from infrared spectra of samples with known ester concentrations.
Using infrared spectroscopy, the average ester content of wax taken
from the synthesis zone of a Fischer-Tropsch reactor with external
continuous hydrogen treatment capability was determined with and
without external continuous hydrogen treatment in operation.
EXAMPLE NO. 1
Synthesis of the Fischer-Tropsch Wax External Continuous Hydrogen
Treatment.
A mixture of hydrogen and carbon monoxide synthesis gas (H.sub.2
:CO=2.1:1) was converted to heavy paraffins in the slurry bubble
column reactor vessel of a multi vessel HCS unit with treatment
means to remove catalyst de-activating species from circulating
slurry similar that that disclosed by Hsia in U.S. Pat. No.
5,260,239. The catalyst utilized was a titania supported cobalt
rhenium catalyst similar to that described in U.S. Pat. No.
4,568,663. The reaction was conducted at 210.degree. C. and 18 bar.
The feed was introduced at a linear velocity of 16.7 cm/sec. The CO
conversion was 50 percent. Hydrogen was introduced at about 40
standard liters (15.degree. C., 1 atm) per minute. The system
provided a slurry conduit valve which was in a closed position,
thus placing the reactor's external hydrogen treatment capabilities
in a non-operative mode. Fischer-Tropsch wax from the reactor was
withdrawn and analyzed. The average ester content, which reflects
the oxygenate content of the wax, is shown in Table 1 below.
Average ester content is based on elemental oxygen.
Under conditions similar to those in Example 1, the slurry conduit
valve was placed in an open position thus enabling the continuous
external hydrogen treatment capabilities of the reactor. Hydrogen
gas was introduced into the treatment zone at about 90 standard
liters (15.degree. C., 1 atm) per minute and the resulting average
ester content of the Fischer-Tropsch wax withdrawn from the reactor
was determined. The results are listed in Table 1.
TABLE 1 External Continuous Example Hydrogen Treatment Means
Average Ester Content No. 1 Off 3.5 .mu.moles/gram-wax No. 2 On
0.50 .mu.moles/gram-wax
From the results recorded in Table 1, it is observed that the ester
content of the wax decreased when the external continuous hydrogen
treatment means was operating, thus demonstrating direct
purification of the circulating slurry containing Fischer-Tropsch
wax which was then drawn directly from the reactor.
In a slurry HCS process the mole ratio of the H.sub.2 to CO is
typically about 1.7 to 2.3. The slurry liquid in the reactor
comprises the hydrocarbon products produced by the hydrocarbon
synthesis reaction which are liquid at the reaction conditions. The
temperature and pressure in the slurry can vary widely depending on
the particular catalyst used and products desired. Typically, for
the production of preferred hydrocarbons comprising predominantly
Fischer-Tropsch waxes (preferably C.sub.10 +paraffins), a supported
cobalt catalyst is employed. The slurry typically contains from
about 10 wt. % to 70 wt. % catalyst solids, more typically from 30
wt. % to 60 wt. % and in some embodiments 40 wt. % to 55 wt. % is
preferred. While catalyst particle sizes may broadly range from as
small as 1 to as large as 200 microns, a typical conventional Fe or
supported iron catalyst will have a mean particle size of about
20-25 microns, while a catalyst comprising a catalytic metal such
as cobalt composited with or supported on titania will typically
have a mean particle size of about 50-70 microns.
In Fischer-Tropsch hydrocarbon synthesis methods useful with
present invention process, the synthesis reaction is carried out
under shifting or non-shifting conditions and preferably under
non-shifting conditions in which little or no water gas shift
reaction occurs, particularly when the catalytic metal comprises
Co, Ru or mixture thereof. Suitable Fischer-Tropsch catalyst
comprises, for example, one or more Group VIII catalytic metals
such as Fe, Ni, Co, Ru and Re. In one embodiment the catalyst
comprises catalytically effective amounts of Co and one or more of
Re, Ru, Fe, Ni, Th, Zr, Hf, U, Mg and La on a suitable inorganic
support material, preferably one which comprises one or more
refractory metal oxides. Preferred supports for Co containing
catalysts comprise titania, particularly when employing a slurry
HCS process in which higher molecular weight, primarily paraffinic
liquid hydrocarbon products, such as Fischer Tropsch waxes are
desired. Useful catalysts and their preparation are known and
illustrative, but nonlimiting examples may be found, for example,
in U.S. Pat. Nos. 4,568,663; 4,663,305; 4,542,122; 4,621,072 and
5,545,674.
* * * * *